At present, mobile phones with large touch screens, particularly smart mobile phones with touch screens, have become the mainstream of the personal terminal market, and moreover, the size of the screens is tending to increase continuously. Enlarged touch screens, while enabling a good user experience in many aspects, also bring a few problems to users. For example, under the influence of usage habits and touch detection algorithms, the character selection accuracy of a user when using virtual keys on a virtual keyboard is worse than the character selection accuracy when using a physical keyboard. Moreover, there is another factor amplifying the effect of this disadvantage, that is, some users are used to operating with a single hand, however, operating with a single hand would easily result in the problem of error input when the user selects the virtual key in a relatively far area on the screen.